Researchers from the University of Illinois Urbana-Champaign have achieved photopumped lasing from a buried dielectric photonic-crystal surface-emitting laser (PCSEL) emitting at room temperature and an eye-safe wavelength. According to the researchers, the work represents an improvement upon current laser design while opening avenues for defense applications. PCSELs are a type of semiconductor laser that uses a photonic crystal layer to produce a laser beam with highly desirable characteristics such as high brightness and narrow, round spot sizes. This type of laser is useful for defense applications such as lidar for battlefield mapping, navigation, and target tracking. PCSELs are typically fabricated using air holes, which become embedded in the device after semiconductor material regrows around the perimeter. However, atoms of the semiconductor tend to rearrange themselves and fill in these holes, compromising the integrity and uniformity of the photonic crystal structure. To combat this problem, the researchers swapped the air holes for a solid dielectric material to prevent the photonic crystal from deforming during regrowth. By embedding silicon dioxide inside the semiconductor regrowth as part of the photonic crystal layer, researchers were able to show the first proof of concept design of a PCSEL with buried dielectric features. “The first time we tried to regrow the dielectric, we didn’t know if it was even possible,” said Erin Raftery, a graduate student in electrical and computer engineering and the lead author of the paper describing the work. “Ideally, for semiconductor growth, you want to maintain that very pure crystal structure all the way up from the base layer, which is difficult to achieve with an amorphous material like silicon dioxide. But we were actually able to grow laterally around the dielectric material and coalesce on top.” The achievement validates that dielectric features can be embedded within epitaxial semiconductors and contribute to the device’s active lasing mechanism. The concept has the potential to broadly apply to various nanophotonic device designs, offering a new tool for exploring innovative design possibilities. According to the researchers, in the next 20 years, these lasers will be used in autonomous vehicles, laser curing, welding, and free space communication. In the meantime, the team will continue to improve on their current design, recreating the same device with electrical contacts allowing the laser to be plugged into a current source for power. The research was published in IEEE Photonics Journal (www.doi.org/10.1109/JPHOT.2025.3561087).
